A string lamp is widely used for indoor or outdoor decoration as a requisite ornament in festival celebration. The string lamp mainly refers to decorative lamps connected in series in an electrical circuit, and typically has an elongated lamp holder for fixing a lamp bulb and a connecting base for achieving electrical connection between the lamp bulb and a lead wire. A plurality of string lamps are connected with one another in series through lead wire segments with metal conductive terminals fixed at two ends. The conductive terminals of these lead wire segments are inserted into the connecting base from the bottom of the connecting base to be electrically connected with lamp pins of the lamp bulb. However, during the use of the string lamp with this structure for decoration, when the lead wire is subjected to lateral tension relative to the connecting base of the string lamp (the lead wire segment between the adjacent lamp holders is straightened perpendicular to an optical axis), some of the conductive terminals are inclined in the connecting base due to the tension, and finally likely to be pulled out from the bottom of the connecting base, resulting in potential safety hazards or extinguishment and failure of the string lamp, which also does not meet the requirements of American safety regulations. In the prior art, a decorative lamp manufacturer adds a false line on the string lamp, and the false line and the lead wire segment are stranded together, when an electrical wire is subjected to lateral tension, the false line can bear most of a tensile force, and the stress on the end of the lead wire segment and the conductive terminals is very low, so that their positions relative to the inner wall of the connecting base are unlikely to change, and they are unlikely to be pulled out from the bottom of the connecting base. However, if the false line and the lead wire segment are not tightly stranded or copper sheets on the conductive terminals are obliquely embedded into the connecting base, when the electrical wire is subjected to tension, some of the conductive terminals can also be pulled out, resulting in potential safety hazards, and also the beauty and the service life are influenced.